Assuming that you already have an amp with a great dirty channel, so you don't necessarily need a main overdrive/distortion (though feel free to nominate one if it really is your desert island pedal).

I think I'd choose a wah pedal. There's so much more to it than just Kirk Hammett bad behaviour - you can use it stopped as a filter, or you can slowly sweep through to create interesting effects... to me it's just a really expressive pedal that I'd like to have on hand.

What about you lot?

(and don't nobody say "HD500" or "G System" if you own one of those, choose an EFFECT, haha)

If I look at my bass pedalboard top usage list, it would look like this :

1. Tuner2. Envelope Filter3. Overdrive4. Wah

Now the question of desert island is more complex as I would also like not to die out of boredom. That being said, if I was to bring one effects pedal to a desert island - I would go for the "looper" pedal That way I can jam with myself and create endless stuff to keep me entertained.

If I was to gig there, I would probably go with the tuner pedal closely followed by envelope filter.